I. Field of the Invention
The present invention relates to the field of wireless data services. More particularly, the present invention relates to a novel and improved method and system for preventing data loss during a Point-to-Point Protocol (PPP) renegotiation over a Um interface between a wireless communication device (MT2) and a base station/mobile switching center (BS/MSC).
II. Description of Related Art
Internetworking, i.e., the connection of individual local area networks (LANs), has rapidly become very popular. The infrastructure and associated protocols commonly referred to as the xe2x80x9cInternetxe2x80x9d have become well known and widely used. A well known protocol for providing access to the Internet is the Point-to-Point Protocol (PPP) which provides a standard method for transporting multi-protocol datagrams over point-to-point, and is further described in Request for Comment (RFC) 1661, W. Simpson, Editor, dated July 1994, herein incorporated by reference.
PPP includes three main components:
1. a method of encapsulating multi-protocol datagrams;
2. a Link Control Protocol (LCP) for establishing, configuring, and testing a data link connection; and
3. a family of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols.
FIG. 1 illustrates a high-level block diagram of a wireless data communication system in which a mobile terminal (TE2 device) 102 communicates with an interworking function (IWF) 108 via a wireless communication system which includes a wireless communication device (MT2) 104 and Base Station/Mobile Switching Center (BS/MSC) 106. In FIG. 1, the IWF 108 serves as the access point to the Internet. IWF 108 is coupled to, and often co-located with BS/MSC 106, which may be a conventional wireless base station, as is known in the art. TE2 device 102 is coupled to MT2 device 104, which is in wireless communication with BS/MSC 106 and IWF 108.
Many protocols exist which allow data communication between the TE2 device 102 and the IWF 108. For example, Telecommunications Industry Association (TIA)/Electronics Industries Association (EIA) Interim Standard IS-707.5, entitled xe2x80x9cData Service Options for Wideband Spread Spectrum Systems: Packet Data Services,xe2x80x9d published February 1998, and herein incorporated by reference, defines requirements for support of packet data transmission capability on TIA/EIA IS-95 wideband spread spectrum systems, of which BS/MSC 106 and IWF 108 may be a part. IS-707.5 also provides the requirements for communication protocols on the links between the TE2 device 102 and the MT2 device 104 (the Rm interface), between the MT2 device 104 and the BS/MSC 106 (the Um interface), and between the BS/MSC 106 and the IWF 108 (the L interface).
Referring now to FIG. 2, a diagram of the protocol stacks in each entity of the IS-707.5 Relay Model is shown. FIG. 2 corresponds roughly to FIG. 1.4.2.2-1 of IS-707.5. At the far left of the figure is a protocol stack, shown in conventional vertical format, showing the protocol layers running on the TE2 device 102 (e.g., the mobile terminal, laptop or palmtop computer). The TE2 protocol stack is illustrated as being logically connected to the MT2 device 104 protocol stack over the Rm, interface. The MT2 device 104, is illustrated as being logically connected to the BS/MSC 106 protocol stack over the Um interface. The BS/MSC 106 protocol stack is, in turn, illustrated as being logically connected to the IWF 108 protocol stack over the L interface.
As an example of the operation of the protocols of FIG. 2, the Point to Point Protocol (PPPR) protocol 206 encodes packets from the upper layer protocols 202, 204 and transmits them across the Rm interface using the EIA-232 protocol 208 to the EIA-232-compatible port on the MT2 device running the EIA-232 protocol 210. In addition to using the EIA-232 protocol, other protocols may also be used, e.g. USB/IRDA/Bluetooth may be used. The EIA-232 protocol 210 on the MT2 device, receives the packets and passes them to the PPPR protocol 205. The PPPR protocol 205 unframes the packets encapsulated in PPP frames and typically, when a data connection is up, passes the packets to PPPU protocol 215, which frames the packets in PPP frames for transmission to a PPP peer located in the IWF (108). The Radio Link Protocol (RLP) 212 and IS-95 protocol 214, both of which are well known in the art, are used to transmit the packets, which are encapsulated in PPP frames, to the BS/MSC 106 over the Um interface. RLP is a family of radio link protocols. The RLP protocol 212 is defined in IS-707.2, entitled xe2x80x9cData Service Options for Wideband Spread Spectrum Systems: Radio Link Protocolxe2x80x9d, February 1998, herein incorporated by reference, and the IS-95 protocol is defined in IS-95 mentioned above. A complementary RLP protocol 216 and IS-95 protocol 218 in the BS/MSC 106 pass the packets to the relay layer protocol 220 for transmission across the L interface to relay layer protocol 228. PPPU protocol 226 then unframes the received packets and passes them to the network layer protocols 225, which in turn passes them to upper layer protocols 221. As is well known to those skilled in the art, instead of using the RLP protocol, the RLP2 protocol could be used. It is defined in Telecommunications Industry Association (TIA)/Electronics Industries Association (EIA) Interim Standard IS-707A.8, entitled xe2x80x9cData Service Options for Spread Spectrum Systems: Radio Link Protocol Type 2,xe2x80x9d published April 1999. Other RLP protocols which may be used are RLP3 and RLP for CDMA2000.
As described in RFC 1661, the LCP Packets comprise a Configure-Request, a Configure-Ack, a Configure-Nak, and a Configure-Reject. The format of these packets is well known and described in RFC 1661.
The Configure-Request packet is used to negotiate configuration options. All configuration options are always negotiated simultaneously.
The Configuration-Ack packet is transmitted if every configuration option in a received Configuration-Request packet is recognizable and all values are acceptable.
The Configure-Nak packet is sent in response to a Configuration-Request packet when the requested configuration options are recognizable, but some of the values are not acceptable. The Options field of the Configure-Nak packet are filled only with the unacceptable configuration options from the Configure-Request packet. Note that all configuration options are always Nak""d simultaneously.
The Configure-Reject packet is sent when a received Configure-Request includes configuration options that are unrecognizable or are not acceptable for negotiation. The options field of the Configure-Reject contains only the unacceptable configuration options from the Configure-Request.
The following comprises the well-known configuration options, described in RFC 1661, and defined for the PPP LCP protocol:
1. Maximum-Receive-Unit
2. Authentication-Protocol
3. Quality-Protocol
4. Magic-Number
5. Protocol-Field-Compression
6. Address-and-Control-Field-Compression
Internet Protocol Control Protocol (IPCP) is a network control protocol responsible for configuring, enabling, and disabling Internet Protocol (IP) modules on both ends of the PPP link. IPCP is described in Request for Comment (RFC) 1332, xe2x80x9cThe PPP Internet Protocol Control Protocol (IPCP)xe2x80x9d, G. McGregor Merit, May 1992, herein incorporated by reference. IPCP configuration options include:
1. IP-Addresses;
2. IP-Compression-Protocol; and
3. IP-Address
IPCP uses the same option negotiation mechanism as the Link Control Protocol (LCP).
LCP and IPCP Configuration option negotiations occur separately for both the Rm interface and the Um interface. That is, LCP or IPCP configuration option negotiation over one of the Rm and Um interfaces is separate from LCP or IPCP configuration option negotiation over the other of the Rm and Um interfaces. Therefore, the wireless communication device must separately negotiate configuration options over the Rm and Um interfaces. Because the wireless communication device (MT2) is mobile, the wireless communication device (MT2) may move to an area that is served by a different IWF 108. When this happens, a handoff will occur, handing the MT2 device over to the new IWF 108 for service. When a handoff occurs, the LCP and IPCP links must be renegotiated over the Um interface, as discussed above. Because PPP negotiation for the Rm and Um interfaces are independent, PPP renegotiation need only occur on the Um interface.
During PPP renegotiation of the Um interface, data cannot be transferred over the Um interface, however, the TE2 device may continue to send data to the MT2 device over the Rm interface. Thus, it is possible for the MT2 device to receive data over the Rm interface without being able to forward the data over the Um interface. If the PPP renegotiation continues over a long period of time, the MT2 device will no longer be able to process data received over the Rm interface and data loss will occur.
A first embodiment of the present invention is a method and a wireless communication device (MT2) 104 capable of flow controlling data to be sent from the TE2102 device over the Rm interface when PPP renegotiation is occurring over the Um interface. Flow control can be asserted by the MT2 device 104 by means of manipulating electrical signalling of a physical interface between the MT2 device 104 and the TE2 device 102 or by using software flow controlxe2x80x94XON/XOFF.
A second embodiment of the present invention, is a method and a wireless communication device (MT2) 104 for buffering data, received from the TE2 device 102, on the MT2 device 104 during PPP renegotiation of the Um interface.
A third embodiment of the present invention is a method and a wireless communication device (MT2) 104 for buffering data on the MT2 device 104 when PPP renegotiation of the Um interface occurs. When an amount of free buffer space is less than a predetermined threshold, the MT2 device 104 asserts flow control to the TE2 device 102. When PPP renegotiation of the Um interface is not occurring, flow control of the TE2 device 102 over the Rm interface is disabled, thereby allowing data to flow from the TE2 device 102 to the MT2 device 104.
Thus, the present invention provides an improved wireless communication device and an improved method of preventing data loss during PPP renegotiation.